Excitation-autoionization processes in electron-impact ionization ofAu68+

Relativistic electron-impact ionization cross sections have been calculated for ${\mathrm{Au}}^{68+}$. Direct ionization cross sections were computed using a relativistic distorted-wave method. Relativistic distorted-wave electron collisional excitation cross sections and detailed relativistic radiative and Auger rates were calculated in order to determine the contribution of excitation-autoionization processes. Because radiative channels are the predominant decay modes for highly charged heavy ions, the effects of excitation-autoionization processes were expected to be small for ${\mathrm{Au}}^{68+}$. However, we found that these processes enhance the direct ionization cross sections by a factor of 4. This enhancement may be observed in experiments on the electron-beam ion trap in the near future.